This invention relates to a vaporizer for vaporizing liquefied gases, and in particular, to a vaporizer using a capacity control valve for controlling an input flow rate of the liquefied gas, such as liquefied petroleum gas, to the vaporizer.
Vaporizers for the controlled vaporization of liquefied gases are generally known. One electrically heated liquefied petroleum gas (LPG) vaporizer is disclosed in U.S. Pat. No. 4,255,646. Another liquefied gas vaporizer is disclosed in U.S. Pat. No. 4,645,904. Typically, such vaporizers includes a pressure vessel having a liquefied gas inlet near a lower end and a gas vapor outlet near a closed upper end remote from the liquefied gas inlet. A heating core is disposed within the pressure vessel, usually positioned close to the lower end, and typically comprises an electric heating element, but can be of other types.
Various means are known for ensuring that a sufficient flow of liquefied gas is provided to the vaporizer without flooding the vaporizer and saturating the gas vapor at the outlet with liquefied gas. For example, a temperature sensor has been used to measure the temperature of the gas vapor in the gas vapor outlet and close a solenoid valve on the liquefied gas inlet if the outlet temperature becomes low, indicating saturation of the gas vapor. An optical sensor has also been used to sense the presence of liquid in the gas vapor to regulate the inflow of the liquefied gas to the vaporizer.
The vaporizer may also have liquefied gas sensing means communicating with the interior of the pressure vessel near its upper end, below the gas vapor outlet. The liquefied gas sensing means is typically a float switch for sensing the level of liquefied gas in the pressure vessel and controlling a valve to stop the inflow of liquefied gas to the vaporizer. The valve stops the flow of liquefied gas to the liquefied gas inlet before the liquefied gas floods through the outlet of the vaporizer.
It is desirable to have better regulation of the liquefied gas inflow to the vaporizer to prevent saturation or xe2x80x9cfloodingxe2x80x9d at the gas vapor outlet, to generate gas vapor at the gas vapor outlet with the desired temperature, and to promote maximum efficiency of the vaporizer using a reliable and inexpensive control arrangement.
The present invention is embodied in a vaporizer for vaporizing a liquefied gas supplied by a source of liquefied gas and useable with a heat source. The vaporizer includes a heat exchanger having an inlet structured to accept liquefied gas, a heat exchanger portion to boil and superheat the accepted liquefied gas to produce a gas vapor using the heat supplied by the heat source, and an outlet structured to release the gas vapor. A temperature sensor is arranged to sense the temperature of the gas vapor produced by the heat exchanger and produce a sensed temperature pressure in response to the sensed temperature. A pressure sensor is arranged to sense the difference in the sensed temperature pressure and a pressure of the liquefied gas supplied by the source of liquefied gas. A flow regulator valve is arranged to regulate the flow of liquefied gas from the source of liquefied gas to the heat exchanger inlet in response to the pressure sensor sensing the difference in the sensed temperature pressure and the pressure of the liquefied gas supplied by the source of liquefied gas.
In one embodiment, the temperature sensor is arranged to sense the temperature of the gas vapor at the heat exchanger outlet. In the one embodiment the vaporizer further includes a biasing member producing a biasing force to bias the flow regulator to reduce the flow of liquefied gas to the heat exchanger inlet, and an adjustment member arranged to selectively adjust the biasing force produced by the biasing member.
The flow regulator is arranged to increase the flow of liquefied gas to the heat exchanger inlet in response to the pressure sensor sensing the difference in the sensed temperature pressure and the pressure of the liquefied gas supplied by the source of liquefied gas being one of increasing and decreasing, and decrease the flow of liquefied gas to the heat exchanger inlet in response to the pressure sensor sensing the difference in the sensed temperature pressure and the pressure of the liquefied gas supplied by the source of liquefied gas being the other of increasing and decreasing.
In the one embodiment the flow regulator is a valve, particularly, a control valve having a valve body with a liquefied gas inlet chamber and a liquefied gas outlet chamber. The control valve has a valve inlet in fluid communication with the liquefied gas inlet chamber and structured to be coupled to and accept the liquefied gas supplied by the source of liquefied gas, and a valve outlet in fluid communication with the liquefied gas outlet chamber and connected to the heat exchanger inlet. The control valve further includes a valve positioned between the liquefied gas inlet chamber and the liquefied gas outlet chamber, with the valve being movable toward a closed configuration to reduce the flow of liquefied gas from the liquefied gas inlet chamber to the liquefied gas outlet chamber and toward an open configuration to increase the flow of liquefied gas from the liquefied gas inlet chamber to the liquefied gas outlet chamber. The valve being moved toward the closed and open configurations in response to the pressure sensor sensing the difference in the sensed temperature pressure and the pressure of the liquefied gas supplied by the source of liquefied gas.
In one embodiment the control valve is a capacity control valve having a valve body with a thermal expansion chamber, a liquefied gas inlet chamber and a liquefied gas outlet chamber. A diaphragm within the valve body divides the thermal expansion chamber from the liquefied gas inlet chamber. The diaphragm is movable in response to a pressure imbalance in the thermal expansion chamber and the liquefied gas inlet chamber.
In this embodiment the temperature sensor is a temperature sensing member positioned to sense the temperature of the released gas vapor from the heat exchanger outlet and has an expansion fluid therein in fluid communication with the thermal expansion chamber. The capacity control valve further includes a valve inlet in fluid communication with the liquefied gas inlet chamber and structured to be coupled to and accept the liquefied gas supplied by the source of liquefied gas, and a valve outlet in fluid communication with the liquefied gas outlet chamber and connected to the heat exchanger inlet. The capacity control valve further includes a valve positioned between the liquefied gas inlet chamber and the liquefied gas outlet chamber. The valve is movable toward a closed configuration to reduce the flow of liquefied gas from the liquefied gas inlet chamber to the liquefied gas outlet chamber and toward an open configuration to increase the flow of liquefied gas from the liquefied gas inlet chamber to the liquefied gas outlet chamber. The valve is moved toward the closed and open configurations in response to movements of the diaphragm resulting from the differential pressure in the thermal expansion chamber and the liquefied gas inlet chamber, with the pressure in the thermal expansion chamber being dependent on the sensed temperature of the released gas vapor from the heat exchanger outlet and the pressure in the liquefied gas inlet chamber being dependent on the pressure of the liquefied gas supplied by the source of liquefied gas.
In this embodiment the temperature sensing member is a sensing bulb thermally coupled to the heat exchanger outlet and the expansion fluid is communicated to the thermal expansion chamber by a tube in fluid communication with the thermal expansion chamber. The expansion fluid is selected to have saturation properties similar to saturation properties of the liquefied gas supplied by the source of liquefied gas.
The capacity control valve further includes an auxiliary pressure device producing a biasing pressure on the valve to bias the valve toward the closed configuration. The auxiliary pressure device has an adjustment member to adjustably select the biasing pressure produced by the auxiliary pressure device.
The diaphragm and the valve are connected together such that movement of the diaphragm toward the thermal expansion chamber moves the valve toward the closed configuration and movement of the diaphragm toward the liquefied gas inlet chamber moves the valve toward the open configuration.
In some embodiments a second valve is utilized with the control valve controlling operation of the second valve.
A method is also disclosed for vaporizing a liquefied gas. The method includes introducing a quantity of liquefied gas into a heat exchanger at a flow rate; vaporizing the liquefied gas in the heat exchanger to produce a gas vapor; sensing the temperature of the gas vapor produced by the heat exchanger; generating a sensed temperature pressure in response to the sensed temperature; sensing a difference in the sensed temperature pressure and a pressure of the liquefied gas supplied by the source of liquefied gas; and adjusting the flow rate of the liquefied gas into the heat exchanger in response to sensing the difference in the sensed temperature pressure and the pressure of the liquefied gas supplied by the source of liquefied gas.
Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings.